In this post, I want to share reverse engineering using ALOHA (Areal Locations of Hazardous Atmosphere) to model thermal radiation and safe fire distances. The original publication can be downloaded here.
The purpose of the study is to assess safe distance of thermal radiation exposure resulting from a tank fire (pool fire) scenario using ALOHA simulation software.
ALOHA (Areal Locations of Hazardous Atmospheres) is an industry-standard atmospheric dispersion modelling tool developed by the EPA and NOAA to predict how chemical releases spread during industrial accidents. By factoring in chemical properties, storage conditions, and ambient weather, it calculates precise threat zones for toxic plumes, explosions, and pool fires.
About Pool Fire
A pool fire occurs when an accidental release of flammable liquid on land or water ignites, forming a buoyancy-driven, turbulent non-premixed flame. Unlike momentum-dominated fires, pool fires are characterized by low initial momentum and strong buoyancy effects. Historical incident data highlights diked pool fires as a prevalent hazard in the petrochemical industry. Due to their high flame heights and intense thermal radiation, these fires pose severe risks to surrounding personnel and equipment, and can trigger domino effects such as Boiling Liquid Expanding Vapor Explosions (BLEVEs) or Vapor Cloud Explosions (VCEs).
Case Studies
PT X operates storage tank T-2018, which holds liquid hydrocarbons. A failure in T-2018 could cause a pool fire, generating thermal radiation that threatens surrounding areas. To establish effective prevention and mitigation measures, a safety impact assessment is needed to evaluate the risks to both onsite personnel and nearby public facilities. These are the data inputs to ALOHA:
- Chemical name : n-heptane
- Atmospheric condition
- Wind speed : 2.5 m/s, from E (East), measurement height above ground is 2 m
- Ground roughness : urban or forest
- Cloud cover : clear
- Air temperature : 34 oC
- Inversion height option : no inversion
- Humidity : 50%
- Source (tank)
- Tank type & orientation : vertical cylinder
- Tank diameter : 15.2 m
- Tank length : 9.8 m
- State of the chemical : tank contains liquid
- Temperature within tank: 30oC
- Liquid level : 80% full by volume
- Type of tank failure : leaking tank, chemical is burning and forms a pool fire
- Shape of opening : circular opening
- Opening diameter : 10 cm
- Leaking through : hole
- The bottom of the leak : 100 cm
- Maximum puddle diameter : unknown
We will evaluate thermal radiation from pool fire at the following values 6.31 kW/m2, 12.5 kW/m2, and 35 kW/m2. The impact of pool fire incident by radiation parameters is described below.
Results
The pool fire consequence modelling establishes the following thermal radiation hazard zones:
- 12 m radius: High-intensity radiation zone (35 kW/m2) presenting lethal conditions.
- 23 m radius: Severe-hazard zone (12.5 kW/m2), causing extreme pain and potential fatalities.
- 32 m radius: Threshold impact zone (6.31 kW/m2), capable of causing skin burns upon continuous exposure.
A detailed spatial illustration of these thermal radiation contours is presented in figure below.
Because the 6.31 kW/m² thermal radiation contour extends up to 32 meters and if it encompasses offsite residential areas, robust public health and safety safeguards must be implemented. Necessary measures include community education, continuous monitoring, heat-control technologies, emergency response infrastructure enhancements, and, if required, residential relocation to effectively minimize offsite risks.
References:
- Darmawan, Irsal & Sutjiningsih, Dwita & Sugiono, Nana. (2025). ALOHA-Based Simulation of Safe Fire Distances for Community Safety near Industrial Production Facilities. Smart Society. 5. 215-224. 10.58524/smartsociety.v5i2.787.
- Zhang, M., Song, W., Wang, J., & Chen, Z. (2014). Accident consequence simulation analysis of pool fire in fire dike. Procedia Engineering, 84, 565–577. https://doi.org/10.1016/j.proeng.2014.10.469